Mike: The "biggies" that everyone is talking about are the trees and the metaballs. While both are worthwhile additions neither is particularly interesting to me. Note I say "to me". Others will love these. But there are a whole pile of other improvements as long as you can ignore the look of the interface, which I consider to be the height of visual poor taste. Terrain resolutions can be much higher. The windows task bar is honoured. You can now actually categorize your presets (except for the skies- how could they leave that out?). The light lab is a large improvement and the material lab is also better. There are many other features I haven't mentioned and I suspect many more I have not yet discovered. I could go on and on. None of these items are earth shaking by themselves but taken as a whole I would say it is a good thing. For my needs B5 is not a "must have" upgrade and I'm not at all sure that the large price increase is justified. Others will, and have, raved about it and called it the best Bryce upgrade yet. Overall, I don't think you can go wrong by upgrading. For myself, I am interested but not excited.